1. Field of the Invention
The present invention relates generally to RADAR systems and more particularly to the control and steering of RADAR beams and to the arrangement and structure of monopulse feed horn antenna arrays.
2. Description of Related Art
RADAR tracking systems are a fixture in most military arsenals, airports, and weather stations. They may be used to detect incoming projectiles, track aircraft trajectories, and/or locate and track targets of interest.
RADAR systems include transmitter, receiver, and processing portions. RADAR systems also contain one or more antennas, depending on the RADAR type and the intended application, and the antennas are often mechanically steered to detect targets in a certain field of view. Space is a concern in modern RADAR applications, requiring smaller and more efficient RADAR systems. Cost may also be a factor, especially in single-use applications such as RADAR-guided munitions.
Monopulse RADAR is variation of conical scanning RADAR wherein the RADAR signal contains additional information to avoid problems caused by changes in signal strength. Monopulse RADAR systems typically transmit a signal on one antenna beam and simultaneously receive the target's reflected signal with two beams, which provide two simultaneous received signals. The signal strengths and, in some types of monopulse radars, the relative phases of these of received signals are then compared. Unlike other conical scanning systems, which compare a signal return to the mechanical position of the antenna, monopulse systems compare the signal return with two beams. Because the comparison takes place based on a single pulse, the system is called “monopulse.” Since monopulse systems compare a signal with itself, there is no time delay in which signal strength can change. Changes in signal strength during a pulse are possible, but they are usually extremely short in duration and have a minimal effect on pulse detection capabilities. Monopulse radar systems also provide increased angle-of-arrival accuracies and faster angle-tracking rates.
Once the RADAR system locates a target, the location information may be sent to a pointing system that will, as appropriate, mechanically re-orient the RADAR antenna so that the boresight will be aligned with the target. Monopulse RADAR technology of this type currently enjoys wide use and is found in several forms of disposable ordinance, including missiles and other guided munitions.
Specifically with respect to RADAR-guided munitions, a mechanical steering solution may have some limitations. There are a number of moving parts that, given the high-impact operating environment most munitions occupy, may be susceptible to failure and malfunction due to mechanical stresses. Also, the number of overall components leads to increases in both cost and weight. For a single-use item such as a missile, reduced cost is an obvious advantage and reduced weight may either increase operating range or reduce fuel requirements.
A RADAR system capable of steering its main lobe for purposes of target acquisition and tracking without mechanical servos and actuators would allow for the production of RADAR-guided munitions of reduced cost and increased reliability. A monopulse RADAR system that does not require a mechanical steering solution may be lighter and less expensive to produce, making it a more attractive option for aerospace applications and single-use applications.